Cancer Tied to Lower AD Risk in Vets

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This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

New research in war veterans adds to a growing body of evidence that cancer is associated with a reduced risk of Alzheimer's disease, and treatment with chemotherapy appears to further lower that risk.

Note that among veterans with a cancer history, treatment with chemotherapy, but not radiation, reduced Alzheimer's risk by 20% to 45%, depending on cancer type, with the exception of prostate cancer.

BOSTON -- New research in war veterans adds to a growing body of evidence that cancer is associated with a reduced risk of Alzheimer's disease (AD), and treatment with chemotherapy appears to further lower that risk.

In a study of more than 80,000 veterans diagnosed with AD during a median follow-up of 5.65 years, most types of cancer were associated with reduced Alzheimer's risk, ranging from 9% to 51%, reported Laura Frain, MD, from the VA Boston Healthcare System, and colleagues.

Additionally, AD was less frequent in veterans with a history of cancer than in those without: 24% versus 76%, the group stated in a presentation at the Alzheimer's Association International Conference in Boston.

"While more and more studies suggest a possible association of cancer with reduced risk for Alzheimer's disease, little is known about whether the association differs between cancer types or is modified by cancer treatment," Frain said.

So the researchers analyzed the health records of 3.5 million veterans, ages 65 and older, who were seen in the VA healthcare system between 1996 and 2011. Participants were free of dementia at baseline.

Over a median follow-up of 5.65 years, 82,028 veterans were diagnosed with Alzheimer's. A total of 771,285 (22%) of the veterans were diagnosed with cancer before or after study baseline.

After adjustment, the following cancers were associated with reduced risk of AD:

Liver cancer: 51% lower risk

Pancreatic cancer: 44%

Cancer of the esophagus: 33%

Myeloma: 26%

Lung cancer: 25%

Leukemia: 23%

Cancers that did not confer a reduced Alzheimer's risk, or were associated with an increased risk, included melanoma, prostate, and colorectal cancers.

Frain told MedPage Today she thinks that is most likely due to increased screening of these types of cancer. "Most of these patients would never have known they had the cancer during their lifetime had they not been screened," she explained.

The researchers also found that among veterans with a cancer history, treatment with chemotherapy, but not radiation, reduced Alzheimer's risk by 20% to 45%, depending on cancer type, with the exception of prostate cancer.

"Recent experimental studies support this finding," said Frain, noting that "cancer and AD cells behave so similarly that some people have called Alzheimer's the cancer of the brain. Cells affected by AD try to divide and in that way act very much like cancer cells and chemotherapy may prevent them from dividing," she said.

"The results of this study are interesting because they could help focus future research onto the specific pathways and treatment agents involved in the individual cancers that are associated with a reduced risk of Alzheimer's," Frain added. "This could potentially open new therapeutic strategies for Alzheimer's prevention and treatment."

David S. Knopman, MD, from the Mayo Clinic, said these are "important observational findings. However, much more study is needed before any therapeutic implications can be drawn," he said.

Frain reported no conflicts of interest.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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